An Improved Self-Consistent-Charge Density-Functional Tight-Binding (SCC-DFTB) Set of Parameters for Simulation of Bulk and Molecular Systems Involving Titanium.

A new self-consistent-charge density-functional tight-binding (SCC-DFTB) set of parameters for Ti-X pairs of elements (X = Ti, H, C, N, O, S) has been developed. The performance of this set has been tested with respect to TiO2 bulk phases and small molecular systems. It has been found that the band structures, geometric parameters, and cohesive energies of rutile and anatase polymorphs are in good agreement with the reference DFT data and with experiment. Low-index rutile and anatase surfaces were also tested. For molecular systems, binding and atomization energies close to their DFT analogues have been achieved. Large errors, however, have been found for systems in high-spin states and/or having multireference character of their wave functions. The correct performance of SCC-DFTB for surface reactions has been demonstrated via the water splitting on anatase (001) surface. The current SCC-DFTB set is a suitable tool for future in-depth investigation of chemical processes occurring on the surfaces of TiO2 polymorphs as well as for other processes of physicochemical interest.